Clinical comparison of single-shot EPI, readout-segmented EPI and TGSE-BLADE for diffusion-weighted imaging of cerebellopontine angle tumors on 3 tesla

Comparison of DWI techniques in patients with epidermoid cyst: TGSE-BLADE DWI vs. SS-EPI DWI

PURPOSE

To compare quantitative values and image quality between single-shot echo-planar imaging (SS-EPI) diffusion-weighted imaging (DWI) and two-dimensional turbo gradient- and spin-echo DWI with non-Cartesian BLADE trajectory (TGSE-BLADE DWI) in patients with epidermoid cyst.

METHODS

Patients with epidermoid cyst who underwent both SS-EPI DWI and TGSE-BLADE DWI were included in this study. Two raters placed ROIs encircling the entire epidermoid cyst on SS-EPI DWI, and then on TGSE-BLADE DWI. Apparent diffusion coefficient (ADC) of the epidermoid cyst was measured within each ROI, then the intraclass correlation coefficient (ICC) between raters was obtained for each DWI. The areas of ROIs placed by the two raters were measured and compared using the Dice coefficient. In the selected slice analysis, one rater selected the most appropriate slice and carefully placed the ROIs slightly smaller than the epidermoid outline to avoid artifacts. Image quality analysis was assessed qualitatively for geometric distortion, susceptibility artifacts, lesion conspicuity, and diagnostic confidence. ADCs for both DWI techniques were compared with theoretical values derived from the diffusion phantom.

RESULTS

Twenty patients with epidermoid cyst were included in this study. The ICC of ADC measured by the two raters for TGSE-BLADE (0.80) was higher than that for SS-EPI (0.59). Dice coefficient of ROI areas was significantly higher with TGSE-BLADE (0.78) than with SS-EPI (0.71, P = 0.007). Selected slice analysis showed that the ADC of epidermoid cyst was significantly higher with TGSE-BLADE DWI than with SS-EPI DWI (P < 0.001). ADCs measured from carefully selected ROIs avoiding artifacts with the two techniques correlated positively (r = 0.87, P < 0.001; ICC 0.75). TGSE-BLADE DWI rated better for image quality than SS-EPI DWI according to all raters. ICCs of measured ADC and theoretical ADCs exceeded 0.99 for both techniques.

CONCLUSIONS

TGSE-BLADE DWI appears more suitable than SS-EPI DWI for evaluating epidermoid cyst.

Comparison of SS-EPI DWI and one-minute TGSE-BLADE DWI for diagnosis of acute infarction

The efficacy of 2D turbo gradient- and spin-echo diffusion-weighted imaging with non-Cartesian BLADE trajectory (TGSE-BLADE DWI) has not been well studied for acute stroke due to its long acquisition time. This study was performed to compare distortion, artifacts and image quality between single-shot echo planar imaging (SS-EPI) DWI and TGSE-BLADE DWI with acquisition time reduced to 1 min by simultaneous multi-slice (SMS) imaging, and to evaluate the diagnostic performance of TGSE-BLADE DWI for acute infarctions. Total 104 patients with a past history of stroke or symptoms suspicious for acute infarction or who had undergone surgery for brain tumor within two days were prospectively enrolled. Ten lesions in 9 patients were diagnosed as acute or subacute infarction and were detectable only in TGSE-BLADE DWI but not in SS-EPI DWI. Scores for geometric distortion, susceptibility artifacts, overall image quality, lesion conspicuity and diagnostic confidence were lower for SS-EPI DWI than TGSE-BLADE DWI (p ≤ .001). Distortion was significantly worse in SS-EPI DWI than TGSE-BLADE DWI (p < .001). SNR of centrum semiovale was significantly higher in SS-EPI DWI than TGSE-BLADE DWI (p < .001). One-minute TGSE-BLADE DWI showed better image quality than SS-EPI DWI in terms of distortion and artifacts, and higher diagnostic performance for acute infarctions.

Thin-slice reverse encoding distortion correction DWI facilitates visualization of non-functioning pituitary neuroendocrine tumor (PitNET)/pituitary adenoma and surrounding normal structures

BACKGROUND

To evaluate the clinical usefulness of thin-slice echo-planar imaging (EPI)-based diffusion-weighted imaging (DWI) with an on-console distortion correction technique, termed reverse encoding distortion correction DWI (RDC-DWI), in patients with non-functioning pituitary neuroendocrine tumor (PitNET)/pituitary adenoma.

METHODS

Patients with non-functioning PitNET/pituitary adenoma who underwent 3-T RDC-DWI between December 2021 and September 2022 were retrospectively enrolled. Image quality was compared among RDC-DWI, DWI with correction for distortion induced by B0 inhomogeneity alone (B0-corrected-DWI), and original EPI-based DWI with anterior-posterior phase-encoding direction (AP-DWI). Susceptibility artifact, anatomical visualization of cranial nerves, overall tumor visualization, and visualization of cavernous sinus invasion were assessed qualitatively. Quantitative assessment of geometric distortion was performed by evaluation of anterior and posterior displacement between each DWI and the corresponding three-dimensional T2-weighted imaging. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and apparent diffusion coefficient values were measured.

RESULTS

Sixty-four patients (age 70.8 ± 9.9 years [mean ± standard deviation]; 33 females) with non-functioning PitNET/pituitary adenoma were evaluated. In terms of susceptibility artifacts in the frontal and temporal lobes, visualization of left trigeminal nerve, overall tumor visualization, and anterior displacement, RDC-DWI performed the best and B0-corrected-DWI performed better than AP-DWI. The right oculomotor and right trigeminal nerves were better visualized by RDC-DWI than by B0-corrected-DWI and AP-DWI. Visualization of cavernous sinus invasion and posterior displacement were better by RDC-DWI and B0-corrected-DWI than by AP-DWI. SNR and CNR were the highest for RDC-DWI.

CONCLUSIONS

RDC-DWI achieved excellent image quality regarding susceptibility artifact, geometric distortion, and tumor visualization in patients with non-functioning PitNET/pituitary adenoma.

RELEVANCE STATEMENT

RDC-DWI facilitates excellent visualization of the pituitary region and surrounding normal structures, and its on-console distortion correction technique is convenient. RDC-DWI can clearly depict cavernous sinus invasion of PitNET/pituitary adenoma even without contrast medium.

KEY POINTS

• RDC-DWI is an EPI-based DWI technique with a novel on-console distortion correction technique. • RDC-DWI corrects distortion due to B0 field inhomogeneity and eddy current. • We evaluated the usefulness of thin-slice RDC-DWI in non-functioning PitNET/pituitary adenoma. • RDC-DWI exhibited excellent visualization in the pituitary region and surrounding structures. • In addition, the on-console distortion correction of RDC-DWI is clinically convenient.

Restaging MRI of Rectal Adenocarcinoma after Neoadjuvant Chemoradiotherapy: Imaging Findings and Potential Pitfalls

Rectal adenocarcinoma constitutes about one-third of all colorectal adenocarcinoma cases. Rectal MRI has become mandatory for evaluation of patients newly diagnosed with rectal cancer because it can help accurately stage the disease, impact the choice to give neoadjuvant therapy or proceed with up-front surgery, and even direct surgical dissection planes. Better understanding of neoadjuvant chemoradiotherapy effects on rectal tumors and recognition that up to 30% of patients can have a pathologic complete response have opened the door for the nonsurgical "watch-and-wait" management approach for rectal adenocarcinoma. Candidates for this organ-preserving approach should have no evidence of malignancy on all three components of response assessment after neoadjuvant therapy (ie, digital rectal examination, endoscopy, and rectal MRI). Hence, rectal MRI again has a major role in directing patient management and possibly sparing patients from unnecessary surgical morbidity. In this article, the authors discuss the indications for neoadjuvant therapy in management of patients with rectal adenocarcinoma, describe expected imaging appearances of rectal adenocarcinoma after completion of neoadjuvant therapy, and outline the MRI tumor regression grading system. Since pelvic sidewall lymph node dissection is associated with a high risk of permanent genitourinary dysfunction, it is performed for only selected patients who have radiologic evidence of sidewall lymph node involvement. Therefore, the authors review the relevant lymphatic compartments of the pelvis and describe lymph node criteria for determining locoregional nodal spread. Finally, the authors discuss limitations of rectal MRI, describe several potential interpretation pitfalls after neoadjuvant therapy, and emphasize how these pitfalls may be avoided. ^© RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Evaluation of apparent diffusion coefficient of two-dimensional BLADE turbo gradient- and spin-echo diffusion-weighted imaging with a breast phantom

This study aimed to evaluate the reliability of apparent diffusion coefficient (ADC) values generated with two-dimensional turbo gradient- and spin-echo with BLADE trajectory diffusion-weighted imaging (TGSE-BLADE-DWI) sequence using a breast diffusion phantom. TGSE-BLADE-DWI and single-shot spin-echo echo-planar imaging (SS-EPI-DWI) were performed using a 3.0 T magnetic resonance imaging scanner. Concordance rates of ADC values and the signal-to-noise ratio (SNR) were compared between TGSE-BLADE-DWI and SS-EPI-DWI. TGSE-BLADE-DWI provided a higher concordance rate for ADC values than SS-EPI-DWI when b-values > 2000s/mm² and a slice thickness of 1 mm were used. TGSE-BLADE-DWI showed less image distortion than SS-EPI-DWI. The SNR of TGSE-BLADE-DWI was higher than that of SS-EPI-DWI, except at a number of excitations of 7 and a slice thickness of 1 mm. In conclusion, TGSE-BLADE-DWI can offer a better SNR, less distortion, and more reliable ADC measurements than SS-EPI-DWI in a breast phantom.

Turbo Gradient and Spin-Echo BLADE-DWI for Extraocular Muscles in Thyroid-Associated Ophthalmopathy

Purpose: To investigate feasibility and diagnostic performance of turbo gradient and spin-echo BLADE (proprietary name for Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction [PROPELLER] in Siemens MR systems)-diffusion weighted imaging (TGSE-BLADE-DWI) for depicting extraocular muscle (EOM) involvement and activity in thyroid-associated ophthalmopathy (TAO), and to compare TGSE-BLADE-DWI with readout-segmented echo-planar imaging (RESOLVE). Materials and methods: Thirty-five patients with identified TAO underwent the two DWI scans. Two radiologists visually scored the image quality of the two DWIs with respect to the susceptibility artifacts and geometric distortions on a three-point scale. The maximum size (Size_max) of EOMs and corresponding ADCs (cADCs) of each patient were compared between the active and inactive phases. The clinical activity score (CAS) was used as a reference to assess the diagnostic performance of EOM ADCs for grading TAO activity. ROC analysis, Pearson correlation, and Wilcoxon signed-rank test were used for statistical analyses. Results: For scores of EOMs, the image quality of TGSE-BLADE-DWI was significantly higher than that of RESOLVE. There were no statistically significant differences between the AUCs of the two DWIs, Size_max, or cADCs between the active and inactive phases. TGSE-BLADE-DWI ADCs were significantly higher than the RESOLVE ADCs in the right superior rectus, right lateral rectus, left superior rectus, and left inferior rectus. There were no statistically significant correlations between the cADC or Size_max, and CAS. The highest AUC was 0.697 for RESOLVE and 0.657 for TGSE-BLADE-DWI. The best performing ADC threshold was 1.85 × 10^-3 mm²/s with 85.7% sensitivity, 58.8% specificity and 66.67% accuracy for RESOLVE and 1.99 × 10^-3 mm²/s with 79.0% sensitivity, and 55.6% specificity and 65.27% accuracy for TGSE-BLADE-DWI. Conclusion: Compared to RESOLVE, TGSE-BLADE-DWI provided improved image quality with fewer susceptibility artifacts and geometric distortions for EOM visualization and showed an equivalent performance in detecting active TAO.

Comparison of TGSE-BLADE DWI, RESOLVE DWI, and SS-EPI DWI in healthy volunteers and patients after cerebral aneurysm clipping

Diffusion-weighted magnetic resonance imaging is prone to have susceptibility artifacts in an inhomogeneous magnetic field. We compared distortion and artifacts among three diffusion acquisition techniques (single-shot echo-planar imaging [SS-EPI DWI], readout-segmented EPI [RESOLVE DWI], and 2D turbo gradient- and spin-echo diffusion-weighted imaging with non-Cartesian BLADE trajectory [TGSE-BLADE DWI]) in healthy volunteers and in patients with a cerebral aneurysm clip. Seventeen healthy volunteers and 20 patients who had undergone surgical cerebral aneurysm clipping were prospectively enrolled. SS-EPI DWI, RESOLVE DWI, and TGSE-BLADE DWI of the brain were performed using 3 T scanners. Distortion was the least in TGSE-BLADE DWI, and lower in RESOLVE DWI than SS-EPI DWI near air-bone interfaces in healthy volunteers (P < 0.001). Length of clip-induced artifact and distortion near the metal clip were the least in TGSE-BLADE DWI, and lower in RESOLVE DWI than SS-EPI DWI (P < 0.01). Image quality scores for geometric distortion, susceptibility artifacts, and overall image quality in both healthy volunteers and patients were the best in TGSE-BLADE DWI, and better in RESOLVE DWI than SS-EPI DWI (P < 0.001). Among the three DWI sequences, image quality was the best in TGSE-BLADE DWI in terms of distortion and artifacts, in both healthy volunteers and patients with an aneurysm clip.

Accuracy of 2D BLADE Turbo Gradient- and Spin-Echo Diffusion Weighted Imaging for the Diagnosis of Primary Middle Ear Cholesteatoma

OBJECTIVE

To evaluate the diagnostic accuracy of 2D BLADE turbo gradient- and spin-echo diffusion weighted imaging (TGSE BLADE DWI) for primary middle ear cholesteatoma diagnosis, using qualitative and quantitative methods.

STUDY DESIGN

Retrospective case series.

SETTING

University hospital.

PATIENTS

Participants included those with suspected primary middle ear cholesteatoma after assessment by clinical otorhinolaryngologists combined with magnetic resonance imaging (MRI) examination. Finally, of the 85 ears from 65 patients enrolled in the study, 73 had cholesteatoma, and 12 had otitis media.

INTERVENTION

Two radiologists independently assessed images and measured apparent diffusion coefficient (ADC) values. Sensitivity, specificity and accuracy were evaluated. Kappa (k) statistics, the intraclass correlation coefficient (ICC), the Kolmogorov-Smirnov normality test, the independent t test, and receiver operating characteristic (ROC) analysis were used for statistical analysis. Pair-wise comparison of the area under the ROC curve (AUC) was also performed using the Delong test.

MAIN OUTCOME MEASURES

Imaging and histopathologic findings.

RESULTS

The mean ADC value of cholesteatoma group (mean, 0.923 ± 0.246 × 10 -3 mm 2 /s) was significantly lower than that of noncholesteatoma group (mean, 1.744 ± 0.205 × 10 -3 mm 2 /s; p < 0.001). In ≤3 mm cholesteatoma group, the AUC of qualitative DWI was 0.846; the sensitivity, specificity, and accuracy for diagnosing cholesteatoma were 69.23%, 100%, and 84%, respectively; while the AUC of quantitative diagnosis was significantly increased to 1.0 ( p = 0.0209); and based on the optimal threshold of ADC, ≤1.352 × 10 -3 mm 2 /s, the sensitivity, specificity and accuracy improved to 100%. For >3 mm cholesteatoma group, there were no significant differences in diagnostic performance. Excellent interobserver agreement and ICC for the qualitative and quantitative evaluations (k = 0.90 and ICC = 0.80, respectively) was noted between reviewers.

CONCLUSION

TGSE BLADE DWI is useful for the detection of primary middle ear cholesteatomas, especially ≤3 mm lesions.

Detection of cholesteatoma: 2D BLADE turbo gradient- and spin-echo imaging versus readout-segmented echo-planar diffusion-weighted imaging

PURPOSE

This study is to compare the accuracy of 2D BLADE turbo gradient- and spin-echo imaging (TGSE BLADE) diffusion-weighted imaging (DWI) with that of readout-segmented echo-planar (RESOLVE) DWI in the detection of primary and residual/recurrent temporal bone cholesteatoma.

METHODS

The prospective study population consisted of 58 patients who were underwent magnetic resonance (MR) imaging for the evaluation of suspected temporal bone cholesteatoma. Two radiologists independently evaluated the two sequences. Kappa (k) statistics, the intra-class correlation coefficient (ICC), and a paired t test were used for statistical analysis.

RESULTS

Of the 58 patients included, all had histo-pathologically confirmed cholesteatomas. In ≤ 3 mm group (n = 13), TGSE BLADE sequence correctly identified all cases except one that was recorded as equivocal on both sequences because of high signal intensity on T1WI; while on RESOLVE sequences, 6 were positive, 4 were equivocal, and 3 were false negative. For > 3 mm group (n = 45), detection performance was similar between the two sequences. The mean ADC of cholesteatoma on TGSE BLADE DWI was 0.923 × 10^-3 mm²/s, and the mean ADC of cholesteatoma on RESOLVE DWI was 0.949 × 10^-3 mm²/s, with no significant difference in the mean ADC values of cholesteatoma measured on the two sequences (p = 0.9216).

CONCLUSION

TGSE BLADE outperforms RESOLVE in the detection of small temporal bone cholesteatoma ≤ 3 mm.

Turbo Gradient and Spin Echo PROPELLER-Diffusion Weighted Imaging for Orbital Tumors: A Comparative Study With Readout-Segmented Echo-Planar Imaging

Purpose: To qualitatively and quantitatively compare the image quality and diagnostic performance of turbo gradient and spin echo PROPELLER diffusion-weighted imaging (TGSE-PROPELLER-DWI) vs. readout-segmented echo-planar imaging (rs-EPI) in the evaluation of orbital tumors.

Materials and Methods: A total of 43 patients with suspected orbital tumors were enrolled to perform the two DWIs with comparable spatial resolution on 3T. The overall image qualities, geometric distortions, susceptibility artifacts, and lesion conspicuities were scored by using a four-point scale (1, poor; 4, excellent). Quantitative measurements, including contrast-to-noise ratios (CNRs), apparent diffusion coefficients (ADCs), geometric distortion rates (GDRs), and lesion sizes, were calculated and compared. The two ADCs for differentiating malignant from benign orbital tumors were evaluated. Wilcoxon signed-rank test, Kappa statistic, and receiver operating characteristics (ROC) curves were used.

Results: TGSE-PROPELLER-DWI performed superior in all subjective scores and quantitative GDR evaluation than rs-EPI (p < 0.001), and excellent interobserver agreement was obtained for Kappa value ranging from 0.876 to 1.000. ADC_lesion of TGSE-PROPELLER-DWI was significantly higher than those of rs-EPI (p < 0.001). Mean ADC of malignant tumors was significantly lower than that of benign tumors both in two DWIs. However, the AUC for differentiating malignant and benign tumors showed no significant difference in the two DWIs (0.860 vs. 0.854, p = 0.7448). Sensitivity and specificity could achieve 92.86% and 72.73% for TGSE-PROPELLER-DWI with a cutoff value of 1.23 × 10^–3 mm²/s, and 85.71% and 81.82% for rs-EPI with a cutoff value of 0.99 × 10^–3 mm²/s.

Conclusion: Compared with rs-EPI, TGSE-PROPELLER-DWI showed minimized geometric distortion and susceptibility artifacts significantly improved the image quality for orbital tumors and achieved comparable diagnostic performance in differentiating malignant and benign orbital tumors.